Week 9
Introduction to Human and Robot Movement
Focus on understanding human movement to develop optimal movement models for humans and robots.
Aims for high speed, efficiency, load-bearing capabilities, and rehabilitation.
Question posed: What constitutes an optimal human or robot for various types of movement?
Understanding Actuation and Control of Movement
Steps to Understanding Movement
Know How We Move: Understand the mechanisms behind human movement.
Develop Structural Requirements: Consider if muscles and tendons need different structures based on movement types.
Examining neuronal roles in biomechanics, while keeping the focus on muscles and tendons mostly.
Brain Control of Movement
The brain orchestrates movement through various structures:
Cerebellum: Major role in movement pattern development, contains most neurons.
Motor Planning Areas: Located in the frontal lobe, these areas generate motor patterns.
Motor Cortex: Central to initiating movement; sends signals down the brain stem to spinal cord.
Motor Neurons: Elicit muscle activation by projecting from the spinal cord to muscles.
Feedback Loops: Sensory information returns to the brain for modulation of movements.
Mechanisms of Movement Feedback
Movement modulated by real-time feedback to optimize performance.
Types of reflexes include:
Monosynaptic Reflex: Quick response, e.g., stabilizing when rolling an ankle.
Multisynaptic Reflexes: Slower responses involving higher brain processing.
Considerations for Optimal Movement
Nervous System and Brain Requirements
For simple tasks like walking:
Focus on optimizing movement timing for muscle activation.
For more complex tasks (high loads/speeds):
Maximal Activation: Motor cortex must be maximally active.
Coordination and timing of muscle activation must be precise.
Understanding how inhibition affects muscle activation is crucial for rehabilitation.
Muscle Activation Levels
Achieving maximum muscle activation is rare due to:
Need for coordination across the entire body during complex tasks.
Moreover, variation in muscle strength and pre-activation levels must be managed carefully.
The Role of Tendons in Movement
Importance of Tendon Compliance
Compliance: Tendency for a structure to deform under a force.
Stiffness vs. Compliance: Stiff tendons resist deformation, whereas compliant tendons stretch easily.
Stiffness helps to store energy better at high forces while compliant tendons are better for low forces and longer ranges of motion.
Energy Storage in Tendons
Compliant tendons can store and return large amounts of elastic energy.
Energy stored is dependent on both stiffness and distance of deformation (E = rac{1}{2} k x^2).
Tendons with higher compliance allow greater energy storage due to enhanced deformation.
Low hysteresis: Loss of energy during loading/unloading is minimal.
Interactions between Muscle Activation and Tendon Properties
Muscle behavior changes based on tendon compliance:
Stiff tendons require higher force and activation for the same range of motion, suitable for short, powerful movements.
Compliant tendons allow lower force applications, making them preferable for endurance tasks or long-range movements.
Training and Conditioning Implications
Optimizing Muscle and Tendon Interactions
Training should aim to increase central nervous system drive to enhance muscle activation while reducing inhibitory signals.
It involves fostering facilitatory reflexes like stretch reflex for maximum performance.
Strategic adjustments may be required to maintain balance between stiffness and compliance relative to a task (e.g., explosive sports vs. endurance activities).
Individual Variations in Tendon Properties
Different individuals have different tendon stiffness and compliance influenced by genetics and training.
Strategies to adjust tendon properties may enhance performance.
Understanding the role of tendon stiffness in athletic performance and injury rehabilitation could lead to tailored training regimens.
Conclusion
Training programs should incorporate understanding of both the neurological and mechanical properties underlying movement Quality.
An optimized human or robot for specific tasks must balance muscle architecture, tendon compliance, and neural drive to achieve peak performance.
Future directions include developing specific training protocols for rehabilitation and enhancing athletic performance based on insights from biomechanics.
ONE PAGE NOTES
Introduction to Human and Robot Movement
Focus on understanding human movement to develop optimal movement models for humans and robots, aiming for high speed, efficiency, load-bearing, and rehabilitation.
Question: What constitutes an optimal human or robot for various types of movement?
Understanding Actuation and Control of Movement
Steps to Understanding Movement
Know How We Move: Understand human movement mechanisms.
Develop Structural Requirements: Consider how muscles, tendons, and neuronal roles influence structure for different movement types.
Brain Control of Movement
The brain orchestrates movement through:
Cerebellum: Major role in movement pattern development, contains most neurons.
Motor Planning Areas (frontal lobe): Generate motor patterns.
Motor Cortex: Initiates movement; sends signals to the spinal cord.
Motor Neurons: Project from spinal cord to muscles, eliciting activation.
Feedback Loops: Sensory information returns to the brain for movement modulation.
Mechanisms of Movement Feedback
Movement is optimized by real-time feedback through reflexes:
Monosynaptic Reflex: Quick, direct response (e.g., stabilizing an ankle roll).
Multisynaptic Reflexes: Slower responses involving higher brain processing.
Considerations for Optimal Movement
Nervous System and Brain Requirements
Simple tasks (e.g., walking): Focus on optimizing muscle activation timing.
Complex tasks (high loads/speeds):
Require maximal motor cortex activation.
Demand precise coordination and timing of muscle activation.
Understanding inhibition's effect on muscle activation is crucial for rehabilitation.
Muscle Activation Levels
Achieving maximum muscle activation is rare due to the need for whole-body coordination and variations in individual muscle strength and pre-activation levels.
The Role of Tendons in Movement
Importance of Tendon Compliance
Compliance: Tendency of a structure to deform under force.
Stiffness vs. Compliance:
Stiff tendons: Resist deformation, better for storing energy at high forces.
Compliant tendons: Stretch easily, better for low forces and longer ranges of motion.
Energy Storage in Tendons
Compliant tendons can store and return large amounts of elastic energy. Energy stored depends on stiffness and deformation distance (E=12kx2E=21kx2).
Higher compliance allows greater energy storage due to enhanced deformation, with minimal energy loss (low hysteresis).
Interactions between Muscle Activation and Tendon Properties- DO FROM HERE
Muscle behavior varies with tendon compliance:
Stiff tendons: Require higher force and activation for the same range of motion, suitable for short, powerful movements.
Compliant tendons: Allow lower force applications, preferable for endurance tasks or long-range movements.
Training and Conditioning Implications
Optimizing Muscle and Tendon Interactions
Training should increase central nervous system drive to enhance muscle activation and reduce inhibitory signals.
Foster facilitatory reflexes (e.g., stretch reflex) for maximum performance.
Strategic adjustments are needed to balance tendon stiffness and compliance based on task demands (e.g., explosive sports vs. endurance).
Individual Variations in Tendon Properties
Tendon stiffness and compliance vary among individuals (genetics, training).
Strategies to adjust tendon properties can enhance performance.
Understanding tendon stiffness in athletic performance and injury rehabilitation leads to tailored training.
Conclusion
Training programs must integrate neurological and mechanical properties of movement.
An optimized human or robot for specific tasks balances muscle architecture, tendon compliance, and neural drive for peak performance.
Future directions include developing specific training protocols for rehabilitation and enhancing athletic performance based on biomechanics insights.